The objective of this program is the development of an inexpensive, reliable, and versatile instrument for the analysis of in vitro cell populations. The instrument will be able to measure (1) cell number, (2) mean cell size, and (3) subcellular structural detail, while the cells remain undisturbed in the standard plastic culture dish. Temporal changes in cell paramenters can be easily monitored. The instrument utilizes laser illumination and functions by detecting and analyzing the angular distribution of the light scattered by the cells. The feasibility of this approach was successfully demonstrated with suspension and monolayer cultures in Phase l. In Phase II OPTRA intends to analyze a wide variety of cell types in order to optimize the performance of the instrument. OPTRA also plans to demonstrate the advantages of the instrument for automating cytotoxicity bioassays. In a parallel collaborative study with a scientist at MIT, comparative tests of a teratogen screening assay will be undertaken using both the newly developed instrument and the conventional laboratory technique. The potential commercial applications for this instrument include a wide range of in vitro research procedures as well as dose-response assays for pharmaceutical and government use.